Once-daily dosing

The antiviral mechanism of action of acyclovir has been reviewed (72). Acyclovir is converted to the monophosphate in herpes vims-infected cells (but only to a limited extent in uninfected cells) by viral-induced thymidine kinase. It is then further phosphorylated by host cell guanosine monophosphate (GMP) kinase to acyclovir diphosphate [66341 -17-1], which in turn is phosphorylated to the triphosphate by unidentified cellular en2ymes. Acyclovir triphosphate [66341 -18-2] inhibits HSV-1 viral DNA polymerase but not cellular DNA polymerase. As a result, acyclovir is 300 to 3000 times more toxic to herpes vimses in an HSV-infected cell than to the cell itself. Studies have shown that a once-daily dose of acyclovir is effective in prevention of recurrent HSV-2 genital herpes (1). HCMV, on the other hand, is relatively uninhibited by acyclovir. 

Initial daily doses of 10-40 and 100-600 mg are recommended in clinical practice for MMI and PTU, respectively [1, 2]. Several studies have shown that treatment of hyperthyroidism with single daily doses of 10-40 mg of MMI is effective in the induction of euthyroidism in 80-90% of patients within 6 weeks [2]. The aim of the further antithyroid therapy is to maintain euthyroidism with the lowest necessary diug dose. Intrathyroidal diug accumulation is one cause for the efficiency of a single daily dose regimen. Moreover, a once daily dose yields better patients compliance. Single daily doses of PTU have been shown to be less effective in achieving euthyroidism than administration of three divided doses a day. If a once daily... 

Anastrazole is a nonsteroidal, type H, aromatase inhibitor that is 200 times more potent than aminoglutethimide. It is eliminated primarily via hqDatic metabolism, has a terminal half life of 50 h with steady state concentrations achieved approximately 10 days with once daily dosing regimens. It is administered orally at a dose of 1 mg/day that achieves near maximal aromatase inhibition and hence estrogen suppression in breast cancer patients. No effect on adrenal steroidogenesis has been observed at up to ten times the daily recommended dose. When used in the metastatic setting, anastrozole has been shown... 

A nurse is to administer nizatidine once daily. When would the nurse most correctly administer the once-daily dose of nizatidine ... 

Ator NA, Weerts EM, Kaminski BJ, et al Zaleplon and triazolam physical dependence assessed across increasing doses under a once-daily dosing regimen in baboons. Drug Alcohol Depend 61 69-84, 2000... 

Typically, statins are the medications of choice to treat high LDL cholesterol because of their ability to substantially reduce LDL cholesterol, ability to reduce morbidity and mortality from atherosclerotic disease, convenient once-daily dosing, and low risk of side effects. 

Monotherapy with a PPI is not only more effective in patients not responding to an H2RA or prokinetic agent alone, but it also improves compliance with once-daily dosing and is ultimately more cost-effective. 

Dosage formulation. Immediate-release formulations of terazosin and doxazosin are quickly absorbed and produce high peak plasma levels. Modified- or extended-release formulations of doxazosin, alfuzosin, and tamsulosin produce lower peak levels, but more sustained therapeutic plasma levels, than immediate-release formulations and have less potential for producing hypotensive episodes, thereby allowing initiation of treatment with a therapeutic dose and once daily dosing.25-27... 

Data for once-daily dosing of aminoglycosides for children exist, but no data for treatment of IE exist. 

Reserpine has a long half-life that allows for once-daily dosing, but it may take 2 to 6 weeks before the maximal antihypertensive effect is seen. 

Most patients require standard doses to prevent relapses. H2RAs may be an effective maintenance therapy in patients with mild disease. The PPIs are the drugs of choice for maintenance treatment of moderate to severe esophagitis. Usual once-daily doses are omeprazole 20 mg, lansoprazole 30 mg, rabeprazole 20 mg, or esomeprazole 20 mg. Lower doses of a PPI or alternate-day regimens may be effective in some patients with less severe disease. 

Doses can be started at 400 mg to 600 mg/day in divided doses, and increased by 200 mg/day every 2 to 4 days up to 10 to 15 mg/kg/day. Outpatients should be titrated upward more slowly to avoid side effects. Many patients are able to tolerate once daily dosing once their mood episode has stabilized. 

Initial side effects are often dose related and are worse at peak serum concentrations (1 to 2 hours postdose). Lowering the dose, taking smaller doses with food, using extended-release products, and once-daily dosing at bedtime may help. 

Muscle weakness and transient lethargy occur in about 30% of patients. Polydipsia with polyuria and nocturia occurs in up to 70% of patients and is managed by changing to once-daily dosing at bedtime. 

Lithium-induced nephrotoxicity is rare if patients are maintained on the lowest effective dose, if once-daily dosing is used, if good hydration is maintained, and if toxicity is avoided. 

Lithium is usually initiated with low to moderate doses (600 mg/day divided into two to three doses) for prophylaxis, and higher doses (900 to 1,200 mg/day, divided into two to three doses) for acute mania. Immediate-release preparations should be given two to three times daily, whereas extended-release products can be given once or twice daily. After patients are stabilized, many patients can be switched to once-daily dosing. 

A 12-hour postdose clozapine serum concentration of at least 250 ng/mL is recommended for patients taking divided doses of clozapine, or 350 ng/ mL if the patient is taking once-daily dosing. 

Inhaled corticosteroids are the preferred long-term control therapy for persistent asthma in all patients because of their potency and consistent effectiveness they are also the only therapy shown to reduce the risk of death from asthma. Comparative doses are included in Table 80-3. Most patients with moderate disease can be controlled with twice-daily dosing some products have once-daily dosing indications. Patients with more severe disease require multiple daily dosing. Because the inflammatory response of asthma inhibits steroid receptor binding, patients should be started on higher and more frequent doses and then tapered down once control has been achieved. The response to inhaled corticosteroids is delayed symptoms improve in most patients within the first 1 to 2 weeks and reach maximum improvement in 4 to 8 weeks. Maximum improvement in FEVj and PEF rates may require 3 to 6 weeks. 

This degree of inhibition correlated with maximal efficacy in preclinical models. Once daily dosing is supported by a half-life of 8-14 h. Using l4C-labeled compound oral bioavailability was found to be 87% [39]. 

Lasix , a loop diuretic drug, is known to be used with a loading dose of 40 mg qd. If it is desired to maintain a once daily dose, how much maintenance dose would you recommend if its half-life is one hour ... 

Pharmacokinetic/pharmacodynamic modeling indicates that the AUC/MIC ratio is predictive of outcome for this antibacterial suggesting that telithromycin is suitable for short-duration therapy and a once-daily dosing regimen even against / -lactam and macrolide-resistant pathogens... 

The purpose of this study is to determine whether once-daily dosing of the lopinavir/ritonavir (Kaletra) tablet in combination with investigator-selected nucleoside/nucleotide reverse transcriptase inhibitors will reduce HIV viral load to very low levels in patients who have detectable viral loads with their current antiretroviral therapy. 

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